Increasing tensile or compressive stress in a semiconductor device substrate can improve drive current. For example, increasing the tensile stress in the substrate can improve the performance of n-channel metal-oxide-semiconductor (NMOS) devices. Similarly, increasing the compressive stress in the substrate can improve the performance of p-channel metal-oxide-semiconductor (PMOS) devices. However, such tuning of the stress in a substrate incorporating NMOS and PMOS devices, such as by increasing tensile stress in substrate regions containing NMOS devices and increasing compressive stress in substrate regions containing PMOS devices, is difficult.
Some applications have realized limited localized stress tuning by employing different materials for adjacent shallow trench isolation (STI) regions and other isolation structures. Stress tuning can also be accomplished by employing different materials for silicide and other contact layers. Etch stop layers remaining in the device structure after being employed as etching endpoints have also been employed for substrate stress tuning. However, such past attempts accomplished only increased tensile stress or increased compressive stress. That is, the performance of PMOS devices in a complimentary metal-oxide-semiconductor (CMOS) scheme were improved, or the performance of NMOS devices in the CMOS scheme were improved, but the past attempts failed to simultaneously improve device performance of both the PMOS and NMOS devices.